CN110234723B

CN110234723B - Conductive adhesive

Info

Publication number: CN110234723B
Application number: CN201880010785.7A
Authority: CN
Inventors: 青柳庆彦; 矶部修; 上农宪治
Original assignee: Tatsuta Electric Wire and Cable Co Ltd
Current assignee: Tatsuta Electric Wire and Cable Co Ltd
Priority date: 2017-08-07
Filing date: 2018-08-02
Publication date: 2023-02-28
Anticipated expiration: 2038-08-02
Also published as: TW201910465A; KR102321279B1; JPWO2019031393A1; TWI713845B; WO2019031393A1; KR20200035910A; CN110234723A; US10723920B2; JP6748783B2; US20200040231A1

Abstract

The conductive adhesive contains a thermosetting resin (A), a conductive filler (B), and an embeddability improver (C). The thermosetting resin (A) contains a first resin component (A1) having a first functional group and a second resin component (A2) having a second functional group that reacts with the first functional group, and the embeddability improver (C) is composed of an organic salt and is 40 to 140 parts by mass per 100 parts by mass of the thermosetting resin.

Description

Conductive adhesive

Technical Field

The present disclosure relates to a conductive adhesive.

Background

In flexible printed wiring boards, conductive adhesives are often used. For example, it is known that: an electromagnetic wave shielding film having a shielding layer and a conductive adhesive layer is bonded to a flexible printed wiring board. In this case, the conductive adhesive is required to firmly adhere an insulating film (cover lay) and a shield layer provided on the surface of the flexible printed wiring board, and to ensure good conduction with a ground circuit exposed from an opening provided in the insulating film.

In recent years, along with the miniaturization of electric equipment, it has been required to secure conductivity by embedding a conductive adhesive in a small opening. Therefore, studies have been made to improve embeddability of the conductive adhesive (see, for example, patent document 1).

Patent document 1: international publication No. 2014/010524.

Disclosure of Invention

Technical problems to be solved by the invention

However, the embeddability of the conventional conductive adhesive cannot be said to be sufficient. The conductive adhesive is required to have not only embeddability but also adhesion.

The technical problem of the present disclosure is to realize a conductive adhesive that can improve embeddability and improve adhesion.

Technical solution for solving the technical problem

In one aspect of the present invention, a conductive adhesive includes a thermosetting resin (a), a conductive filler (B), and an embeddability improver (C), the thermosetting resin (a) includes a first resin component (A1) having a first functional group and a second resin component (A2) having a second functional group that reacts with the first functional group, the embeddability improver (C) is composed of an organic salt, and the embeddability improver (C) is 40 parts by mass or more and 140 parts by mass or less with respect to 100 parts by mass of the thermosetting resin.

In the conductive adhesive of the invention of the one aspect, the embeddability improver (C) may be a metal salt of phosphinic acid (metal salt of phosphinic acid).

In this case, the median particle diameter of the metal phosphinate can be set to 5 μm or less.

In the conductive adhesive according to one aspect of the present invention, the first functional group may be an epoxy group, the glass transition temperature of the second resin component (A2) may be 5 ℃ to 100 ℃, the number average molecular weight of the second resin component (A2) may be 1 ten thousand to 5 ten thousand, and the second resin component (A2) may have a functional group that reacts with the epoxy group.

In the conductive adhesive of the invention of one aspect, the second resin component (A2) may be a urethane-modified polyester resin (urethane-modified polyester resin).

In one aspect of the present disclosure, an electromagnetic wave-shielding film includes a protective layer and a conductive adhesive layer made of the conductive adhesive of the present disclosure.

In the reinforcing plate for a printed wiring board according to the invention of one aspect of the present disclosure, the reinforcing plate for a printed wiring board includes a conductive reinforcing plate and a conductive adhesive layer formed of the conductive adhesive of the present disclosure provided on at least one surface of the conductive reinforcing plate.

The shielded printed wiring board of the present disclosure has a base member (base member) having a ground circuit, a cover layer covering the ground circuit, the cover layer having an opening portion exposing a part of the ground circuit, and an electromagnetic wave shielding film having a conductive adhesive layer made of the conductive adhesive of the present disclosure.

In one aspect of the present disclosure, a printed wiring board includes a base member, a cover layer, a conductive reinforcing plate, a conductive adhesive layer, and an electronic component, wherein a ground circuit is provided on at least one surface of the base member, the cover layer covers the ground circuit, an opening portion for exposing a part of the ground circuit is provided in the cover layer, the conductive reinforcing plate is disposed to face the ground circuit, the conductive adhesive layer bonds the ground circuit and the conductive reinforcing plate in a conductive state, the electronic component is disposed at a position of the base member corresponding to the conductive reinforcing plate, and the conductive adhesive layer is composed of the conductive adhesive of the present disclosure.

Effects of the invention

According to the conductive adhesive of the present disclosure, embeddability and adhesiveness can be improved.

Drawings

Fig. 1 is a cross-sectional view showing one example of an electromagnetic wave shielding film.

Fig. 2 is a cross-sectional view showing a modification of the electromagnetic wave shielding film.

Fig. 3 (a) to 3 (c) are sectional views sequentially showing a method for manufacturing an electromagnetic wave shielding film.

Fig. 4 is a sectional view showing the shield printed wiring board.

Fig. 5 is a sectional view showing one manufacturing process of the shield printed wiring board.

Fig. 6 is a cross-sectional view showing a step of bonding the conductive reinforcing plate.

Fig. 7 is a cross-sectional view showing a step of bonding the conductive reinforcing plate.

Fig. 8 is a cross-sectional view showing a step of bonding the conductive reinforcing plates.

Fig. 9 is a diagram showing a measurement method of the interconnect resistance.

Fig. 10 is a graph showing the temperature dependence of the loss elastic modulus.

Fig. 11 is a graph showing the temperature dependence of the storage elastic modulus.

Detailed Description

The conductive adhesive of the present embodiment includes a thermosetting resin (a), a conductive filler (B), and an embeddability improver (C). The thermosetting resin (a) includes a first resin component (A1) having a first functional group and a second resin component (A2) having a second functional group that reacts with the first functional group. The embeddability improver (C) is composed of an organic salt, and is 40 to 140 parts by mass per 100 parts by mass of the thermosetting resin.

-thermosetting resin (A) -

The first resin component (A1) of the thermosetting resin (a) has 2 or more first functional groups in 1 molecule. The first functional group may be any functional group as long as it reacts with the second functional group included in the second resin component (A2), and may be, for example, an epoxy group, an amide group, a hydroxyl group, or the like, with an epoxy group being preferred.

When the first functional group is an epoxy group, as the first resin component (A1), the following can be used: bisphenol epoxy resins such as bisphenol a epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin; spiro epoxy resin (spirocyclic epoxy resin); naphthalene type epoxy resins; biphenyl type epoxy resin; terpene type epoxy resins; glycidyl ether type epoxy resins such as Tris (glycidyl ether oxyphenyl) methane (Tris (glycidyl ether oxyphenyl) methane), tetrakis (glycidyl ether oxyphenyl) ethane (tetrakis (glycidyl ether oxyphenyl) ethane); glycidyl amine type epoxy resins such as tetraglycidyl diaminodiphenylmethane; tetrabromobisphenol a type epoxy resin (tetrabromobisphenol a epoxy resin); cresol novolac type epoxy resins; phenol novolac epoxy resin (phenol novolac epoxy resin); alpha-naphthol novolac type epoxy resin; phenolic epoxy resins such as brominated phenolic novolak epoxy resins; rubber-modified epoxy resins, and the like. These may be used alone or in combination of two or more. The epoxy resin may be solid or liquid at normal temperature. In the case of an epoxy resin, "solid at room temperature" means a state that does not have fluidity at 25 ℃ in a state of no solvent, and "liquid at room temperature" means a state that has fluidity under the same conditions.

The first resin component (A1) is not particularly limited, and the number average molecular weight is preferably 500 or more, and more preferably 1000 or more, from the viewpoint of improving the bulk strength of the adhesive. From the viewpoint of adhesion, the number average molecular weight is preferably 10000 or less, and more preferably 5000 or less.

The second resin component (A2) has a second functional group that reacts with the first functional group of the first resin component (A1). In the case where the first functional group is an epoxy group, the second functional group can be a hydroxyl group, a carboxyl group, an epoxy group, an amino group, or the like. Among them, hydroxyl group and carboxyl group are preferable. In the case where the first functional group is an amide group, the second functional group can be a hydroxyl group, a carboxyl group, an amino group, or the like. In addition, in the case where the first functional group is a hydroxyl group, the second functional group can be an epoxy group, a carboxyl group, an amino group, or the like.

In the case where the second functional group is a carboxyl group, the second resin component (A2) can be, for example, a urethane-modified polyester resin. The urethane-modified polyester resin is a polyester resin containing a polyurethane resin as a copolymer component. The urethane-modified polyester resin can be obtained, for example, by condensation-polymerizing an acid component such as a polycarboxylic acid or an anhydride thereof and a glycol component to obtain a polyester resin and then reacting a terminal hydroxyl group of the polyester resin with an isocyanate component. Further, it is also possible to react the acid component, the glycol component, and the isocyanate component at the same time to obtain the urethane-modified polyester resin.

<xnotran> , (terephthalic acid), (isophthalic acid), (orthophthalic acid), 1,5- (1,5-naphthalenedicarboxylic acid), 2,6- ,4,4 ' - (4,4 ' -diphenyldicarboxylic acid), 2,2' - ,4,4 ' - (4,4 ' -diphenyletherdicarboxylic acid), , , ,1,4- (1,4-cyclohexanedicarboxylic acid), 1,3- ,1,2- ,4- -1,2- , , () (dehydrated trimellitic acid), () (dehydrated pyromellitic acid), 5- (2,5- -3- ) -3- -3- -1,2- (5- (2,5-dioxotetrahydro-3-furanyl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride) . </xnotran>

The ethylene glycol component is not particularly limited, and for example, ethylene glycol, propylene glycol (propylene glycol), 1,3-propanediol (1, 3-propanediol), 2-methyl-1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 3-methyl-1, 5-pentanediol, neopentyl glycol, diethylene glycol (diethylene glycol), dipropylene glycol (dipropylene glycol), 2, 4-trimethyl-1, 5-pentanediol, cyclohexanedimethanol, neopentyl hydroxypivalate (neopentyl glycol), ethylene oxide adduct and propylene oxide adduct of bisphenol A, ethylene oxide adduct and propylene oxide adduct of hydrogenated bisphenol A, 1, 9-nonanediol, 2-methyloctanediol, 1, 10-decanediol, 2-butyl-2-ethyl-1, 3-cyclohexanediol, tricyclodimethanol (polypropylene glycol), polyethylene glycol, polypropylene glycol, etc., if necessary, a ternary or higher polyhydric alcohol such as trimethylolpropane (trimethylolpropane), trimethylolethane (trimethylolethane), pentaerythritol (pentaerythritol) or the like can be used.

The isocyanate component is not particularly limited, and for example, 2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, 3'-dimethoxy-4,4' -biphenyl diisocyanate (3, 3'-dimethoxy-4,4' -biphenylene diisocyanate), 1,5-naphthalene diisocyanate, 2, 6-naphthalene diisocyanate, 3 '-dimethyl-4, 4' -diisocyanate, 4'-diphenyl ether diisocyanate (4, 4' -diphenylene diisocyanate), 1, 5-xylylene diisocyanate, 1,3 methylcyclohexane diisocyanate, 1, 4-methylcyclohexane diisocyanate, isophorone diisocyanate, and the like can be used.

The second resin component (A2) is not limited to the urethane-modified polyester resin, and an acid anhydride-modified polyester resin, an epoxy resin, or the like can be used.

When a urethane-modified polyester resin is used as the second resin component (A2), the glass transition temperature thereof is preferably 5 ℃ or higher, more preferably 10 ℃ or higher, and still more preferably 30 ℃ or higher, from the viewpoint of further improving embeddability. Further, it is preferably 100 ℃ or lower, more preferably 90 ℃ or lower, and further preferably 80 ℃ or lower. In addition, the glass transition temperature can be measured using a Differential Scanning Calorimetry (DSC).

When a urethane-modified polyester resin is used as the second resin component (A2), the number average molecular weight (Mn) thereof is preferably 1 ten thousand or more and preferably 5 ten thousand or less, and more preferably 3 ten thousand or less, from the viewpoint of further improving the embeddability. In addition, mn can be set to a value in terms of styrene measured by Gel Permeation Chromatography (GPC).

When a urethane-modified polyester resin having a carboxyl group is used as the second resin component (A2), the acid value thereof is preferably 5mgKOH/g or more, more preferably 10mgKOH/g or more, and still more preferably 15mgKOH/g or more, from the viewpoint of heat resistance. Further, it is preferably 50mgKOH/g or less, more preferably 45mgKOH/g or less, and further preferably 40mgKOH/g or less. The acid value may be determined according to JIS K0070:1992 to make measurements.

When the first resin component (A1) is an epoxy resin and the second resin component (A2) is a urethane-modified polyester resin, the ratio (A1/(A1 + A2)) of the first resin component (A1) to the total mass of the first resin component (A1) and the second resin component (A2) can be 1 mass% or more, preferably 3 mass% or more, and the ratio can be 15 mass% or less, preferably 10 mass% or less. By setting the first resin component (A1) and the second resin component (A2) in such a ratio, the adhesion can be improved.

The thermosetting resin (a) can be blended with a curing agent (A3) that promotes a reaction between the first functional group of the first resin component (A1) and the second functional group of the second resin component (A2). The curing agent (A3) can be appropriately selected according to the types of the first functional group and the second functional group. When the first functional group is an epoxy group and the second functional group is a hydroxyl group, an imidazole-based curing agent, a phenol-based curing agent, a cationic curing agent, or the like can be used. These may be used alone or in combination of two or more.

Examples of the imidazole-based curing agent include the following compounds obtained by addition of an imidazole ring to an alkyl group, cyanoethyl (ethylcyanono), hydroxyl group, azine (azine), and the like: 2-phenyl-4, 5-bis (hydroxymethyl) imidazole, 2-heptadecyl imidazole, 2,4-diamino-6- (2 ' -undecylimidazolyl) ethyl-S-triazine, 1-cyanoethyl-2-phenylimidazole, 5-cyano-2-phenylimidazole, 2,4-diamino-6- [2' methylimidazole- (1 ') ] -ethyl-S-triazine isocyanuric acid adduct (2, 4-diamino-6- [2' methylimidazolyl- (1 ') ] -ethyl-S-triazine isocyanuric acid adduct), 2-phenylimidazole isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 1-cyanoethyl-2-phenyl-4, 5-bis (2-cyanoethoxy) methylimidazole, and the like.

Examples of the phenolic curing agent include novolak (novolac phenol) and naphthol compounds.

Examples of the cationic curing agent include amine salts of boron trifluoride, antimony pentachloride-acetyl chloride complex, and sulfonium salts having a phenethyl group or an allyl group.

The curing agent (A3) may not be added, but from the viewpoint of promoting the reaction, the curing agent (A3) is preferably 0.3 parts by mass or more, more preferably 1 part by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, with respect to 100 parts by mass of the first resin component (A1).

Conductive filler (B)

The conductive filler (B) is not particularly limited, and for example, a metal filler, a metal-coated resin filler (metal-coated resin filler), a carbon filler, and a mixture of these fillers can be used. Examples of the metal filler include copper powder, silver powder, nickel powder, silver-coated copper powder (silver-coated copper powder), gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. The metal powder can be produced by an electrolytic method, an atomization method, a reduction method, or the like. Among these, any of silver powder, silver-coated copper powder, and copper powder is preferable.

The conductive filler (B) is not particularly limited, but from the viewpoint of contacting fillers with each other, the average particle diameter is preferably 1 μm or more, more preferably 3 μm or more, and preferably 50 μm or less, more preferably 40 μm or less. The shape of the conductive filler (B) is not particularly limited, and may be spherical, sheet-like, dendritic, or fiber-like, but dendritic is preferable from the viewpoint of obtaining a good interconnection resistance value.

The content of the conductive filler (B) can be appropriately selected according to the use, but is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less in the total solid content. From the viewpoint of embeddability, it is preferably 70% by mass or less, and more preferably 60% by mass or less. When anisotropic conductivity is achieved, the content is preferably 40% by mass or less, and more preferably 35% by mass or less.

Embeddability improver (C)

The embeddability improver (C) is a component that improves embeddability by maintaining the loss elastic modulus of the conductive adhesive within a certain range even at high temperatures. The intercalation property-improving agent (C) can be an organic salt. Among the organic salts, phosphates such as polyphosphates and metal phosphinates are preferable, and metal phosphinates are more preferable. As the metal phosphinate, aluminum salt, sodium salt, potassium salt, magnesium salt, calcium salt, and the like can be used, and among them, aluminum salt is preferable. As the polyphosphate salt, melamine salt, methylamine salt, ethylamine salt, diethylamine salt, triethylamine salt, ethylenediamine salt, piperazine salt, pyridine salt, triazine salt, ammonium salt, and the like can be used, and among them, melamine salt is preferable. As the organic salt other than the phosphate, melamine cyanurate, melamine pyrophosphate, and melam methosultanate (melam methosultate) can be used, and among them, melamine cyanurate is preferable.

From the viewpoint of improving embeddability, the blending amount of the embeddability improver (C) is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and preferably 140 parts by mass or less, more preferably 120 parts by mass or less, further preferably 100 parts by mass or less, and further preferably 80 parts by mass or less, with respect to 100 parts by mass of the thermosetting resin (a).

The embeddability improver (C) preferably does not protrude from the film of the conductive adhesive, and preferably has a smaller particle diameter than the thickness of the film of the conductive adhesive. The median particle diameter of the embeddability modifier (C) varies depending on the thickness of the film to be finally formed, and the median particle diameter of the embeddability modifier (C) can be preferably 5 μm or less, and more preferably 4 μm or less. From the viewpoint of handling, it can be preferably 1 μm or more, more preferably 2 μm or more.

The median diameter is a particle diameter at which the cumulative frequency from the small particle diameter side reaches 50% in a particle size distribution curve (the vertical axis represents cumulative frequency%, and the horizontal axis represents particle diameter) obtained by a laser diffraction particle size distribution measuring apparatus.

Optional components

As optional components, an antifoaming agent, an antioxidant, a viscosity modifier, a diluent, an anti-settling agent, a leveling agent, a coupling agent, a coloring agent, a flame retardant, and the like can be added to the conductive adhesive of the present embodiment.

< first embodiment >

(electromagnetic wave shielding film)

The conductive adhesive of the present disclosure can be applied to the electromagnetic wave shielding film 101 having the protective layer 112 and the conductive adhesive layer 111 shown in fig. 1. Such an electromagnetic wave shielding film can cause the conductive adhesive layer 111 to function as a shielding film. As shown in fig. 2, a shield layer 113 may be provided between the protective layer 112 and the conductive adhesive layer 111.

Protective layer-

The protective layer 112 has sufficient insulating properties, and the protective layer 112 is not particularly limited as long as it can protect the conductive adhesive layer 111 and, if necessary, the shield layer 113, and for example, a thermoplastic resin composition, a thermosetting resin composition, an active energy ray-curable composition, or the like can be used.

The thermoplastic resin composition is not particularly limited, and a styrene-based resin, a vinyl acetate-based resin, a polyester-based resin, a polyethylene-based resin, a polypropylene-based resin, an imide, an acrylic resin composition, or the like can be used. The thermosetting resin composition is not particularly limited, and a phenol-aldehyde resin composition, an epoxy resin composition, a polyurethane resin, a melamine resin composition, an alkyd resin composition, or the like can be used. The active energy ray-curable composition is not particularly limited, and for example, a polymerizable compound having at least 2 (meth) acryloyloxy groups in the molecule, or the like can be used. The protective layer may be formed of a single material or 2 or more materials.

The protective layer 112 may be a laminate of 2 or more layers having different physical properties such as material, hardness, elastic modulus, and the like. For example, in the case of a laminate of an outer layer having a low hardness and an inner layer having a high hardness, the outer layer has a cushioning effect, and therefore, in the step of bonding the electromagnetic wave shielding film 101 to the printed wiring board by heating and pressing the electromagnetic wave shielding film 101, the pressure applied to the shielding layer 113 can be alleviated. Therefore, the shield layer 113 can be prevented from being damaged by the level difference provided on the printed wiring board.

The protective layer 112 may further contain at least one of a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, a viscosity regulator, an anti-blocking agent (anti-blocking agent), and the like, as required.

The thickness of the protective layer 112 is not particularly limited, and the thickness of the protective layer 112 can be appropriately set as needed, but is preferably 1 μm or more, more preferably 4 μm or more, and preferably 20 μm or less, more preferably 10 μm or less, and further preferably 5 μm or less. By setting the thickness of the protective layer 112 to 1 μm or more, the conductive adhesive layer 111 and the shield layer 113 can be sufficiently protected. By setting the thickness of the protective layer 112 to 20 μm or less, the flexibility of the electromagnetic wave shielding film 101 can be ensured, and the electromagnetic wave shielding film 101 can be easily applied to a member requiring flexibility.

Shielding layer-

When the electromagnetic wave shielding film 101 has the shielding layer 113, the shielding layer 113 may be formed of a metal layer, a conductive filler, or the like. In the case of the metal layer, the metal layer may be made of an alloy containing any one or two or more of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, and the like. The metal layer can be manufactured by depositing a metal film using a metal foil or by an additive process (additive process). As the additive method, a plating method, an electroless plating method (electrolytic plating), a sputtering method, an electron beam evaporation method, a vacuum evaporation method, a Chemical Vapor Deposition (CVD) method, a Metal Organic Chemical Vapor Deposition (MOCVD) method, or the like can be used.

When the shield layer 113 is made of a conductive filler, metal nanoparticles or a conductive filler can be used. Examples of the metal nanoparticles include mercury nanoparticles and gold nanoparticles. As the conductive filler, for example, a metal filler, a metal-coated resin filler, a carbon filler, and a mixture of these fillers can be used. The metal filler includes copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder, and the metal powder can be produced by an electrolytic method, an atomization method, and a reduction method. Examples of the shape of the metal powder include a spherical shape, a sheet shape, a fiber shape, and a dendritic shape.

The metal material and thickness of the shield layer 113 may be appropriately selected according to the required electromagnetic shielding effect and repeated bending and sliding resistance, and the thickness may be set to about 0.1 to 12 μm.

In addition, when the electromagnetic wave shielding film 101 has the shielding layer 113, the content of the conductive filler (B) contained in the conductive adhesive that becomes the conductive adhesive layer 111 is preferably 3 mass% or more, and more preferably 5 mass% or more, from the viewpoint of improving the shielding property. From the viewpoint of cost, the upper limit is preferably 40% by mass or less, and more preferably 35% by mass or less.

In the case where the electromagnetic wave-shielding film 101 does not have the shielding layer 113 and the conductive adhesive layer 111 functions as a shield, the content of the conductive filler (B) contained in the conductive adhesive is preferably 40 mass% or more from the viewpoint of ensuring shielding properties. From the viewpoint of the bending resistance of the electromagnetic wave shielding film 101, the upper limit of the conductive filler (B) is preferably 90 mass% or less.

(method for producing electromagnetic wave shielding film)

An example of a method for manufacturing the electromagnetic wave shielding film 101 will be described below, but the manufacturing method is not limited thereto.

Formation of a protective layer

First, as shown in FIG. 3 (a), a composition for a protective layer is applied to a supporting base material 151 to form a protective layer 112. The protective layer composition can be prepared by adding an appropriate amount of solvent and other compounding agents to the resin composition. Examples of the solvent include toluene, acetone, methyl ethyl ketone, methanol, ethanol, propanol, and dimethylformamide. As other compounding agents, a crosslinking agent, a polymerization catalyst, a curing accelerator, a coloring agent, and the like can be added. The other compounding ingredient may be added as needed, or may not be added. The method of applying the composition for a protective layer to the supporting base member 151 is not particularly limited, and known techniques such as lip coating (lip coating), doctor coating (comma coating), gravure coating (gravure coating), or slot-die coating (slot-die coating) can be used.

The supporting base member 151 can be formed in a film shape, for example. The supporting base member 151 is not particularly limited, and the supporting base member 151 may be formed of a material such as polyolefin, polyester, polyimide, polyphenylene sulfide, or the like. A release agent layer may be provided between the supporting base member 151 and the composition for a protective layer.

After the composition for a protective layer is applied to the supporting base material 151, the solvent is removed by heating and drying, thereby forming the protective layer 112. The supporting base member 151 can be peeled off from the protective layer 112. The separation of the supporting base material 151 can be performed after the electromagnetic wave shielding film 101 is attached to the printed wiring board. Thus, the electromagnetic wave shielding film 101 can be protected by the supporting base member 151.

Formation of a barrier layer

Next, as shown in fig. 3 (b), a shield layer 113 is formed on the surface of the protective layer 112. When the shield film 113 is a metal film, the shield layer 113 can be formed by a plating method, an electroless plating method, a sputtering method, an electron beam deposition method, a vacuum deposition method, a CVD method, an MOCVD method, or the like. When the shield layer 113 is made of a conductive filler, the shield layer 113 can be formed by applying a solvent containing the conductive filler to the surface of the protective layer and drying the applied solvent. In the case where the electromagnetic wave shielding film 101 does not include the shielding film 113, this step can be omitted.

Formation of a conductive adhesive layer

Next, as shown in fig. 3 (c), after the conductive adhesive layer composition is applied to the shield layer 113, the conductive adhesive layer 111 is formed by heating and drying to remove the solvent.

The composition for a conductive adhesive layer comprises a conductive adhesive and a solvent. Examples of the solvent include toluene, acetone, methyl ethyl ketone, methanol, ethanol, propanol, and dimethylformamide. The ratio of the conductive adhesive in the composition for a conductive adhesive layer may be appropriately set according to the thickness of the conductive adhesive layer 111 and the like.

The method for applying the composition for a conductive adhesive layer on the shield layer 113 is not particularly limited, and lip coating, knife coating, gravure coating, nip extrusion coating, or the like can be used.

The thickness of the conductive adhesive layer 111 is preferably 1 μm to 50 μm. By setting to 1 μm or more, sufficient embeddability can be achieved, and sufficient connection to a ground circuit can be obtained. Further, by setting the thickness to 50 μm or less, the requirement for a thin film can be satisfied, which is also advantageous in terms of cost.

Further, a release base (release film) may be bonded to the surface of the conductive adhesive layer 111 as necessary. The peeling base member can adopt: a base material prepared by applying a silicon-based or non-silicon-based release agent to the surface of a primary coating such as polyethylene terephthalate or polyethylene naphthalate on which the conductive adhesive layer 111 is to be formed. The thickness of the peeling base material is not particularly limited, and can be determined in consideration of usability.

(Shielding printed Wiring Board)

The electromagnetic wave shielding film 101 of the present embodiment can be used, for example, for shielding a printed wiring board 103 as shown in fig. 4. As shown in fig. 4, the shielding printed wiring board 103 has a printed wiring board 102 and an electromagnetic wave shielding film 101.

The printed wiring board 102 has, for example, a printed circuit including a base member (base member) 122 and a ground circuit 125 provided on the base member 122. The insulating film 121 is adhered to the base member 122 via an adhesive layer 123. The insulating film 121 is provided with an opening 128 for exposing the ground circuit 125. A gold plating layer, i.e., a surface layer 126, is provided on the exposed portion of the ground circuit 125. The printed wiring board 102 may be a flexible substrate or a rigid substrate.

Next, a method for manufacturing the shielded printed wiring board 103 will be described. First, as shown in fig. 5, a printed wiring board 102 and an electromagnetic wave shielding film 101 are prepared.

Next, the electromagnetic wave shielding film 101 is disposed on the printed wiring board 102 so that the conductive adhesive layer 111 is positioned on the opening 128, and temporarily fixed.

Then, the 2 hot plates are pressurized at a predetermined pressure (for example, 3 MPa) for a predetermined time (for example, 30 minutes) at a predetermined temperature (for example, 170 ℃) higher than that at the time of the temporary fixation. This enables the electromagnetic wave shielding film 101 to be fixed to the printed wiring board 102.

At this time, a part of the conductive adhesive layer 111 softened by heating is pressed and flows into the opening 128. Thereby, the shield layer 113 is connected to the ground circuit 125. Since a sufficient amount of the conductive adhesive layer 111 is present between the shield layer 113 and the printed wiring board 102 in the opening 128, the electromagnetic wave shielding film 101 and the printed wiring board 102 are bonded with sufficient strength. Further, since the conductive adhesive layer 111 has high embeddability, connection stability can be ensured even when exposed to high temperatures during reflow (reflow) in the component mounting process.

Thereafter, a reflow process for mounting components is performed. In the reflow step, the electromagnetic wave shielding film 101 and the printed wiring board 102 are exposed to a high temperature of about 260 ℃. The component to be mounted is not particularly limited, and chip components such as resistors and capacitors may be used in addition to connectors and integrated circuits.

The conductive adhesive of the present embodiment has high embeddability, and therefore can be sufficiently embedded in the opening 128 even when the diameter a of the opening 128 is small, for example, when the diameter a is 1mm or less, and can ensure good connection between the electromagnetic wave shielding film 101 and the ground circuit 125. If the embeddability is insufficient, fine bubbles enter between the surface layer 126 and the conductive adhesive layer 111 and between the insulating film 121 and the conductive adhesive layer 111. As a result, when exposed to high temperatures in the reflow step, bubbles grow, which increases the interconnection resistance of the conductive adhesive layer 111, and in the worst case, may peel off. However, the conductive adhesive layer 111 of the present embodiment has excellent adhesion to the surface layer 126 and the insulating film 121, and can maintain good adhesion even after the reflow step, thereby maintaining low interconnection resistance.

The interconnect resistance after reflow, which is an index of embeddability, is preferably as small as possible, and for example, as described in the examples, the interconnect resistance for an opening having a diameter of 0.5mm can be preferably 300m Ω/1 hole or less, more preferably 250m Ω/1 hole or less, and further preferably 200m Ω/1 hole or less.

In order to ensure embeddability of the conductive adhesive, it is preferable that the conductive adhesive maintain a loss elastic modulus in a relatively high range in a temperature range of not lower than the maximum temperature at which the conductive adhesive is heated and not higher than the reflow temperature when the conductive adhesive is attached to the printed wiring board. The maximum temperature reached by heating at the time of bonding can be about 130 to 190 ℃, and the reflow temperature can be about 240 to 260 ℃. Therefore, the loss elastic modulus at 140 ℃ can be made preferably to be 5.0X 10 ⁴ Pa or more, more preferably 7.0X 10 ⁴ Pa or more, and preferably 3.0X 10 ⁵ Pa or less, more preferably 2.5X 10 ⁵ Pa or less. Further, the loss elastic modulus at 170 ℃ can be preferably set to 5.0X 10 ⁴ Pa or more, more preferably 7.0X 10 ⁴ Pa or more, and preferably 4.0X 10 ⁵ Pa or less, furtherPreferably 3.5X 10 ⁵ Pa or less. In addition, the loss elastic modulus at 200 ℃ can be made preferably to be 5.0X 10 ⁴ Pa or more, more preferably 7.0X 10 ⁵ Pa or more, and preferably 4.0X 10 ⁵ Pa or less, more preferably 3.5X 10 ⁵ Pa or less.

In order to ensure embeddability, it is preferable to maintain the storage elastic modulus at a relatively low value in such a temperature range. Specifically, the storage modulus of elasticity at 190 ℃ can be preferably set to 1.0X 10 ⁵ Pa or more, and preferably 2.0X 10 ⁵ Pa or less. Further, the storage modulus of elasticity at 170 ℃ can be preferably set to 1.0X 10 ⁴ Pa or more, and preferably 2.5X 10 ⁵ Pa or less. Further, the storage elastic modulus at 120 ℃ can be preferably 1X 10 ⁵ Pa or more, and preferably 4.0X 10 ⁵ Pa or less. Further, the storage elastic modulus at 70 ℃ can be preferably set to 1.0X 10 ⁵ Pa or more, and preferably 1X 10 ⁶ Pa or less. By setting the storage elastic modulus within the above range, latent stress is less likely to be generated in the conductive adhesive during heating and pressing, and as a result, the embeddability becomes good.

The conductive adhesive of the present disclosure preferably has a maximum value at which a storage elastic modulus curve at 40 to 120 ℃ does not show a significant value greater than a storage elastic modulus at 40 ℃. In this temperature range, the storage elastic modulus curve does not show a maximum value, and therefore, latent stress is less likely to be accumulated in the conductive adhesive during heating and pressing, and as a result, the embeddability becomes good.

From the viewpoint of firmly bonding the electromagnetic wave shielding film 101, the peel strength between the conductive adhesive layer 111 and the surface layer 126 is preferably high, specifically, 3.0N/10mm or more, more preferably 3.5N/10mm or more, and still more preferably 4.0N/10mm or more. Further, the peel strength between the conductive adhesive layer 111 and the insulating film 121 is preferably high, and more specifically, is preferably 3.0N/10mm or more, more preferably 5.0N/10mm or more, and further preferably 7.0N/10mm or more.

The base member 122 can be, for example, a resin film or the like, and specifically can be a film made of a resin such as polypropylene, crosslinked polyethylene, polyester, polybenzimidazole, polyimide, polyamideimide, polyetherimide, or polyphenylene sulfide.

The insulating film 121 is not particularly limited, and may be formed of a resin such as polyethylene terephthalate, polypropylene, crosslinked polyethylene, polyester, polybenzimidazole, polyimide, polyamideimide, polyetherimide, or polyphenylene sulfide. The thickness of the insulating film 121 is not particularly limited, and can be set to about 10 μm to 30 μm.

The printed circuit including the ground circuit 125 can be, for example, a copper wiring pattern formed on the base member 122. The surface layer 126 is not limited to a gold plating layer, and may be a layer made of copper, nickel, silver, tin, or the like. The surface layer 126 may be provided as needed, or the surface layer 126 may not be provided.

The conductive adhesive of the present embodiment is excellent in embeddability and adhesion, and exhibits particularly excellent effects when the electromagnetic wave shielding film 101 is attached to the printed wiring board 102. However, the conductive adhesive is also useful for other applications using the conductive adhesive. For example, the adhesive agent can be used for an adhesive layer of a conductive reinforcing plate.

< second embodiment >

(conductive reinforcing plate)

The conductive adhesive of the present disclosure can be used for mounting a conductive (metal) reinforcing plate to a flexible printed wiring board.

When mounting a conductive reinforcing plate on a printed wiring board, first, as shown in fig. 6, a flexible printed wiring board 104 and a conductive reinforcing plate 135 having a conductive adhesive layer 130 formed of the conductive adhesive of the present embodiment provided on one surface thereof are prepared.

The method of providing the conductive adhesive layer 130 on the surface of the conductive reinforcing plate 135 is, for example, as shown in fig. 7, first applying a conductive adhesive on a release base material (release film) 152 to form a conductive adhesive film 153 having the conductive adhesive layer 130. Next, the conductive adhesive film 153 and the conductive reinforcing plate 135 are pressed and adhered to each other, whereby the conductive reinforcing plate 135 having the conductive adhesive layer 130 as shown in fig. 8 can be obtained. The peeling base member 152 may be peeled off before use.

The peeling base member 152 can employ: a base material obtained by applying a silicon-based or non-silicon-based release agent to the surface of a primary coating such as polyethylene terephthalate or polyethylene naphthalate on which the conductive adhesive layer 130 is to be formed. The thickness of the peeling base member 152 is not particularly limited, and can be determined in consideration of usability.

The thickness of the conductive adhesive layer 130 is preferably 15 μm to 100 μm. By setting to 15 μm or more, sufficient embeddability can be achieved, and sufficient connection with a ground circuit can be obtained. Further, by setting the thickness to 100 μm or less, the requirement for a thin film can be satisfied, which is also advantageous in terms of cost.

The flexible printed wiring board 104 includes, for example, a base member 142 and an insulating film 141 adhered to the base member 142 via an adhesive layer 143. The insulating film 141 is provided with an opening 148 for exposing the ground circuit 145. A gold plating layer, i.e., a surface layer 146, is provided on the exposed portion of the ground circuit 145. In addition, the flexible printed wiring board 104 can be replaced with a rigid substrate.

Next, the conductive reinforcing plate 135 is disposed on the printed wiring board 104 so that the conductive adhesive layer 130 is positioned on the opening 148. Then, the conductive reinforcing plate 135 and the printed wiring board 104 are sandwiched from above and below by 2 hot plates (not shown) heated to a predetermined temperature (for example, 120 ℃) and pressed at a predetermined pressure (for example, 0.5 MPa) for a short time (for example, 5 seconds). Thereby, the conductive reinforcing plate 135 is temporarily fixed to the printed wiring board 104.

Then, the temperature of the 2 hot plates is set to a predetermined temperature (for example, 170 ℃) higher than the above-mentioned temporary fixing time, and the plates are pressurized under a predetermined pressure (for example, 3 MPa) for a predetermined time (for example, 30 minutes). Thus, the conductive reinforcing plate 135 can be fixed to the printed wiring board 104 with the conductive adhesive layer 130 filled in the opening 148.

Thereafter, a reflow process for mounting components is performed. In the reflow step, the flexible printed wiring board 104 is exposed to a high temperature of about 260 ℃. The component to be mounted is not particularly limited, and chip components such as resistors and capacitors may be used in addition to connectors and integrated circuits. When the conductive reinforcing plate 135 is provided on one surface of the base member, the electronic component can be disposed on the surface of the base member 142 opposite to the conductive reinforcing plate 135 in correspondence with the conductive reinforcing plate 135. However, the conductive reinforcing plates 135 may be provided on both surfaces of the base member 142.

Since the conductive adhesive of the present embodiment has high embeddability, even when the diameter of the opening 148 is small, for example, 1mm or less, it can be sufficiently embedded in the opening 148, and good connection between the conductive reinforcing plate 135 and the ground circuit 145 can be ensured. If the embeddability is insufficient, fine bubbles enter between the surface layer 146 and the conductive adhesive layer 130 and between the insulating film 141. As a result, when exposed to high temperatures in the reflow step, bubbles grow, and the interconnect resistance of the conductive adhesive layer 130 increases, and in the worst case, peeling may occur. However, the conductive adhesive layer 130 of the present embodiment has excellent adhesion to the surface layer 146 and the insulating film 141, and can maintain good adhesion even after the reflow step, thereby maintaining low interconnection resistance.

The interconnect resistance after reflow, which is an index of embeddability, is preferably as small as possible, and for example, as described in the examples, the interconnect resistance with respect to an opening having a diameter of 0.5mm can be preferably 300m Ω/1 hole or less, more preferably 250m Ω/1 hole or less, and further preferably 200m Ω/1 hole or less.

The conductive reinforcing plate 135 can be formed of a conductive material having an appropriate strength. The conductive material may contain nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, or the like. Among them, stainless (stainless) is preferable from the viewpoint of corrosion resistance and strength.

The thickness of the conductive reinforcing plate 135 is not particularly limited, but is preferably 0.05mm or more, more preferably 0.1mm or more, and preferably 1.0mm or less, more preferably 0.3mm or less, from the viewpoint of reinforcement.

Further, a nickel layer is preferably formed on the surface of the conductive reinforcing plate 135. The method for forming the nickel layer is not particularly limited, and the nickel layer can be formed by a method such as an electroless plating method or an electroplating method. If a nickel layer is formed, the adhesion between the conductive reinforcing plate and the conductive adhesive can be improved.

When the conductive adhesive of the present disclosure is applied to bonding of a conductive reinforcing plate, it is preferable to have the same property of loss elastic modulus as in the case of an electromagnetic wave shielding film in order to secure embeddability. From the viewpoint of preventing peeling of the conductive reinforcing plate, it is preferable that the electromagnetic wave shielding film has the same peel strength as the electromagnetic wave shielding film.

Examples

Hereinafter, the conductive adhesive of the present disclosure will be described in further detail with reference to examples. The following examples are illustrative and are not intended to limit the invention.

< production of electromagnetic wave shielding film >

An epoxy resin was applied to the release film to a thickness of 6 μm and dried to form a protective layer. Next, predetermined materials were mixed and stirred using a planetary stirring and defoaming device, and conductive adhesive compositions of examples 1 to 3 and comparative examples 1 to 3 having the components shown in table 1 were produced.

Further, the following values were used as the median particle diameter of the embedment property improver: a value measured in a volume distribution mode using a diffraction particle size distribution measuring apparatus (Microtrac S3500 manufactured by Microtrac) and pure water (refractive index = 1.33) as a solvent, with the refractive index of the inorganic particles being 1.51.

Next, a paste-like conductive adhesive composition was applied on the protective layer, and dried at 100 ℃. The thickness of the electromagnetic wave-shielding film was 17 μm before the pressurization and 10 μm after the pressurization. The thickness of the electromagnetic wave-shielding film was measured by a micrometer.

< measurement of loss elastic modulus >

The dynamic viscoelasticity of the conductive adhesive compositions of the examples and comparative examples was measured in a range of 30 to 200 ℃ by a rheometer (MCR 302, manufactured by Anton Paar Co., ltd.), and the loss elastic modulus (G ") at 200 ℃ was determined. As a measurement sample, a sample obtained by forming the conductive adhesive composition into a disc shape having a diameter of 25mm and a thickness of 1mm was used, and the measurement was performed under the following conditions.

D-PP25/AL/S07 flat plate with diameter of 25mm

Deflection angle (Angular deflection) 0.1%

Frequency 1Hz

The measurement range is 30-200 DEG C

The heating rate is 6 ℃/min.

< adhesion to polyimide >

The adhesion between the polyimide and the conductive adhesive was measured by a 180 ° peel test. Specifically, the conductive adhesive layer side of the electromagnetic wave shielding film was bonded to a polyimide film (made by Tolyu-Dupont, kapton100EN (registered trademark)) at a temperature of: 170 ℃ and time: the adhesive was applied for 3 minutes under a pressure of 2 MPa. Next, on the protective layer side of the electromagnetic wave-shielding film, at a temperature: 120 ℃ and time: an adhesive film (manufactured by Botzenkusho Co., ltd.) was adhered under a pressure of 0.5MPa for 5 seconds. Next, a polyimide film (Kapton 100EN (registered trademark)) was bonded to the adhesive film to prepare an evaluation laminate. Then, the polyimide film/adhesive film/shielding film laminate was peeled off from the polyimide film at a rate of 50 mm/min. Table 1 shows the average value with the number of trials set to n = 5.

< adhesion to gold-plated layer >

The adhesiveness between the gold-plated layer formed on the surface of the copper foil of the copper-clad laminate and the conductive adhesive was measured by a 180 ° peel test. Specifically, the conductive adhesive layer side of the electromagnetic wave shielding film is bonded to a gold plating layer provided on the surface of a copper foil laminated film, and the ratio of temperature: 170 ℃ and time: the adhesive was applied for 3 minutes under a pressure of 2 MPa. Next, on the protective layer side of the electromagnetic wave shielding film, at a temperature: 120 ℃ and time: an adhesive film (manufactured by Kouzhikari Co., ltd.) was adhered under a pressure of 0.5MPa for 5 seconds. Subsequently, a polyimide film (Kapton 100H (registered trademark), manufactured by toli-dupont) was bonded to the adhesive film to prepare a laminate for evaluation. Then, the polyimide film/adhesive film/shielding film laminate was peeled from the polyimide film at a rate of 50 mm/min. Table 1 shows the average value with the number of trials set to n = 5.

< manufacture of shielded printed Circuit Board

Next, the electromagnetic wave shielding films produced in the respective examples and comparative examples were bonded to a printed wiring board using a press under the following conditions, temperature: 170 ℃, time: 30 minutes, pressure: 2 to 3MPa.

Further, as the printed wiring board, there were used: as shown in fig. 4, a copper foil pattern 125 similar to a ground circuit is formed on a base member 122 made of a polyimide film, and an insulating adhesive layer 123 and a cover layer (insulating film) 121 made of a polyimide film are formed thereon. A gold plating layer is provided as a surface layer 126 on the surface of the copper foil pattern 125. In addition, the cover layer 121 is formed with an opening 128 simulating a ground connection portion having a diameter a of 0.5 mm.

< measurement of interconnect resistance value >

Using the shielded printed wiring boards produced in the respective examples and comparative examples, as shown in fig. 9, the resistance values between the 2 copper foil patterns 125 having the surface layer 126, which is a gold plating layer, provided on the surface thereof were measured by a resistance meter 205, and the connectivity between the copper foil patterns 125 and the electromagnetic wave shielding film 101 was evaluated as the initial interconnection resistance value (interconnection resistance value before reflow soldering).

Next, the shield printed wiring boards of the manufactured examples and comparative examples were passed through a hot-air reflow apparatus (hot-air reflow) five times, and then the interconnect resistance values after reflow soldering were measured by the above-described method. As the conditions for reflow soldering, the following heating conditions were set: lead-free solder was assumed, and exposure of the polyimide film in the shielded printed wiring board to 265 ℃ for 5 seconds was set.

(example 1)

As the first resin component (A1), a solid epoxy resin having an epoxy equivalent of 700g/eq and a number average molecular weight of 1200 was used. As the second resin component, a urethane-modified polyester resin having Mn of 18000, an acid value of 20mgKOH/g, a glass transition temperature of 40 ℃ and a number average molecular weight of 18000 was used. The ratio (A1/(A1 + A2)) of the first resin component (A1) to the total mass of the first resin component (A1) and the second resin component (A2) was set to 5 mass%. To 100 parts by mass of the first resin component (A1), 6 parts by mass of 2-phenyl-1H-imidazole-4, 5-dimethanol (2 PHZPW, manufactured by the four kingdom chemical industry) was added as a curing agent (A3).

For the conductive filler (B), dendritic (dendritic) silver-coated copper powder (D-1) having an average particle diameter of 13 μm and a silver coating rate of 8 mass% was used. The conductive filler was 55 parts by mass with respect to 100 parts by mass of the thermosetting resin (a).

As the intercalation modifier (C), aluminum tris diethyl phosphinate (aluminum salt of tris (diethylphosphonic acid)) (OP 935, manufactured by Clariant Japan) was used, and 71 parts by mass of the intercalation modifier (C) was used per 100 parts by mass of the thermosetting resin (a).

The peel strength of the obtained conductive adhesive with respect to polyimide was 5.3N/10mm, and the peel strength with respect to gold-plating layer was 8.5N/10mm. Furthermore, the initial interconnect resistance was 145m Ω/1 hole in the case of an aperture of 0.5mm φ, and the interconnect resistance after reflow soldering was 190m Ω/1 hole. The loss elastic modulus at 200 ℃ is 1.3X 10 ⁵ Pa。

(example 2)

The procedure of example 1 was repeated, except that 71 parts by mass of Melamine Cyanurate (Melamine Cyanurate) having an average particle diameter of 2 μm was used as the embedment modifier (C).

The obtained conductive adhesive had a peel strength of 4.1N/10mm with respect to polyimide and a peel strength of 7.8N/1 with respect to gold-plating layer0mm. Furthermore, the initial interconnect resistance was 150m Ω/1 hole for a pore diameter of 0.5mm φ, and the interconnect resistance after reflow soldering was 220m Ω/1 hole. The loss elastic modulus at 200 ℃ is 1.9X 10 ⁵ Pa。

(example 3)

The procedure was carried out in the same manner as in example 1 except that 71 parts by mass of Melamine Polyphosphate (Melamine Polyphosphate) having an average particle diameter of 6 μm was used as the embedment performance improving agent (C).

The peel strength of the obtained conductive adhesive with respect to polyimide was 6.4N/10mm, and the peel strength with respect to gold-plated layer was 9.0N/10mm. Furthermore, the initial interconnect resistance was 150 m.OMEGA./1 via for a 0.5 mm.phi aperture, and the interconnect resistance after reflow soldering was 223 m.OMEGA./1 via. The loss elastic modulus at 200 ℃ is 1.4X 10 ⁵ Pa。

Comparative example 1

The procedure of example 1 was repeated, except that 35.5 parts by mass of aluminum trisdiethylphosphinate (OP 935, manufactured by Clariant Japan) was used as the insertion property improver (C).

The peel strength of the obtained conductive adhesive with respect to polyimide was 7.3N/10mm, and the peel strength with respect to gold-plating was 8.3N/10mm. Furthermore, the initial interconnect resistance was 227m Ω/1 hole in the case of a pore diameter of 0.5mm φ, and the interconnect resistance after reflow soldering was 457m Ω/1 hole. The loss elastic modulus at 200 ℃ was 4.7X 10 ⁴ Pa。

Comparative example 2

The procedure was carried out in the same manner as in example 1 except that 142 parts by mass of aluminum trisdiethylphosphinate (OP 935, manufactured by Clariant Japan) was used as the intercalation property improver (C).

The peel strength of the obtained conductive adhesive with respect to polyimide was 3.3N/10mm, and the peel strength with respect to gold-plating was 7.2N/10mm. The initial interconnect resistance at the aperture diameter of 0.5mm phi is equal to or higher than the measurement limit value (OL), and the interconnect resistance after reflow soldering is also OL. The loss elastic modulus at 200 ℃ was 4.4X 10 ⁵ Pa。

Comparative example 3

The procedure was carried out in the same manner as in example 1 except that the embedment improver (C) was not added.

The peel strength of the obtained conductive adhesive with respect to polyimide was 6.7N/10mm, and the peel strength with respect to gold-plated layer was 6.4N/10mm. Furthermore, the initial interconnect resistance was 814m Ω/1 via for a 0.5mm φ aperture, and the interconnect resistance after reflow soldering was 1780m Ω/1 via. The loss elastic modulus at 200 ℃ is 4.5X 10 ⁴ Pa。

Table 1 shows the components and characteristics of the conductive adhesives of the examples and comparative examples in combination.

[ Table 1]

Fig. 10 shows the temperature dependence of the loss elastic modulus of the conductive adhesives of the examples and comparative examples. The conductive adhesives of examples 1 to 3 maintained appropriate loss elastic modulus in the temperature range of 170 ℃ or higher at which embedding was performed, compared with the conductive adhesives of comparative examples 1 to 3. Fig. 11 shows the temperature dependence of the storage elastic modulus of the conductive adhesives of the examples and comparative examples. The storage elastic modulus curves at 40 ℃ to 120 ℃ of the conductive adhesives of examples 1 to 3 did not show a significant maximum value larger than the storage elastic modulus at 40 ℃.

Industrial applicability-

The conductive adhesive of the present disclosure can improve embeddability and improve adhesion, and is useful as a conductive adhesive used in a flexible printed wiring board or the like.

-description of symbols-

101. Electromagnetic wave shielding film

102. Printed wiring board

104. Printed wiring board

111. Conductive adhesive layer

112. Protective layer

113. Shielding layer

121. Insulating film

122. Base part

123. Adhesive layer

125. Grounding circuit

126. Surface layer

128. Opening part

130. Conductive adhesive layer

135. Conductive reinforcing plate

141. Insulating film

142. Base part

143. Adhesive layer

145. Grounding circuit

146. Surface layer

148. Opening part

151. Supporting base member

152. Stripping base

153. Conductive adhesive film

205. And (4) a resistance meter.

Claims

1. An electrically conductive adhesive, characterized in that: comprises the following steps:

a thermosetting resin (A),

A conductive filler (B),

An embedding property improving agent (C),

the thermosetting resin (A) comprises a first resin component (A1) having a first functional group and a second resin component (A2) having a second functional group that reacts with the first functional group,

the first functional group is an epoxy group,

the second resin component (A2) is a urethane-modified polyester resin,

the embeddability improver (C) is composed of an organic salt, and is 50 to 140 parts by mass with respect to 100 parts by mass of the thermosetting resin (A).

2. A conductive adhesive according to claim 1, wherein:

the embeddability improver (C) is a metal phosphinate.

3. A conductive adhesive according to claim 2, wherein:

the median particle diameter of the metal phosphinate is 5 [ mu ] m or less.

4. A conductive adhesive according to any one of claims 1 to 3, wherein:

the second resin component (A2) has a glass transition temperature of 5 ℃ to 100 ℃, the number average molecular weight of the second resin component (A2) is 1 ten thousand to 5 ten thousand, and the second resin component (A2) has a functional group that reacts with an epoxy group.

5. An electromagnetic wave shielding film, characterized in that:

the electromagnetic wave shielding film comprises a protective layer and a conductive adhesive layer, wherein the conductive adhesive layer is composed of the conductive adhesive according to any one of claims 1 to 4.

6. A printed wiring board reinforcing plate, characterized in that:

the reinforcing plate for a printed wiring board comprises a conductive reinforcing plate and a conductive adhesive layer provided on at least one surface of the conductive reinforcing plate,

the conductive adhesive layer is composed of the conductive adhesive according to any one of claims 1 to 4.

7. A shielded printed wiring board, characterized in that:

the shielded printed wiring board includes a base member, a cover layer and an electromagnetic wave shielding film,

the base member is provided with a ground circuit,

the cover layer covers the ground circuit and is provided with an opening portion for exposing a part of the ground circuit,

the electromagnetic wave-shielding film is adhered to the cover layer,

the electromagnetic wave shielding film has a conductive adhesive layer comprising the conductive adhesive according to any one of claims 1 to 4.

8. A printed wiring board characterized by:

the printed wiring board comprises a base member, a cover layer, a conductive reinforcing plate, a conductive adhesive layer and an electronic component,

a ground circuit is provided on at least one face of the base member,

the conductive reinforcing plate is disposed so as to face the ground circuit,

the conductive adhesive layer bonds the ground circuit and the conductive reinforcing plate in a conductive state,

the electronic component is disposed at a position of the base member corresponding to the conductive reinforcing plate,